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Endangered species update, 13:1/2 (January/February 1996)

University of Michigan, School of Natural Resources
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  • Biology
  • Chemistry
  • Medicine


U P D A T E January/February 1996 Vol. 13 Nos. 1& 2 School of Natural Resources and Environment THE UNIVERSITY OF MICHIGAN In this Issue American Zoo and The Marbled Murrelet: Aquarium Association Looking at Effects of Species Conservation Proposed Changes to the Programs Endangered Species Act The Status of Anadromous The Value of Learning in Atlantic Salmon Endangered Species Conservation Status of Anadromous Atlantic Salmon, Salmo salar, in the United States Mary Colligan and Paul Nickerson Anadromous Atlantic salmon (Salrno salar) migrate from the mouths of U.S. rivers to the Northwest Atlantic Ocean, overwintering in the southern Labrador Sea and the Bay of Fundy. Atlantic salmon begin their lives in riv- ers where they stay for two to three years before beginning the process of smoltification to prepare for migration to the ocean. During smoltification, biochemical and physiological changes prepare the Atlantic salmon for the tran- sition from fresh to salt water. The ocean portion of the species life history typi- cally lasts from one to three years (adults that return after only one year at sea are called grilse), during which they under- take feeding migrations over thousands of miles. Atlantic salmon feed on cape- lin, herring, sandeels and large zooplank- ton (Reddin 1988), and appear to be opportunistic feeders as their numbers are not correlated with the availability of a particular prey species. After returning to spawn, kelts (spawned-out salmon) either re- turn to the ocean or overwinter in the river. Mature adults show a strong affinity for their native river (a straying rate of 2% for hatchery fish over 22 years according to Baum and Spencer 1990), and appear to use olfactory stimuli to return to their native streams (Stasko etal. 1973) between April and November. This strong hom- ing ability has resulted in the evo- lution of unique characteristics for each river population, for ex- ample in the timing

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